Τίτλος:
Effect of different levels of pressure support and proportional assist
ventilation on breathing pattern, work of breathing and gas exchange in
mechanically ventilated hypercapnic COPD patients with acute respiratory
failure
Περίληψη:
Background: Proportional assist ventilation (PAV) has been shown to
maintain better patient-ventilator synchrony than pressure support
ventilation (PSV); however, its clinical advantage regarding invasive
ventilation of COPD patients has not been clarified. Objectives: To
compare the effect of PAV and PSV on respiratory parameters of
hypercapnic COPD patients with acute respiratory failure (ARF). Methods:
Nine intubated hypercapnic COPD patients were placed on the PAV or PSV
mode in random sequence. For each mode, four levels (L-1-L-4) of support
were applied. At each level, blood gases, flow, tidal volume (V-T),
airway pressure (Paw), esophageal pressure (Pes) (n = 7), patient
respiratory rate (fp), ventilator rate (fv), missing efforts (ME = fp -
fv) were measured. Results: We found increases in ME with increasing
levels of PSV but not with PAV. PO2 and V-T increased whereas PCO2
decreased significantly with increasing levels of PSV (p < 0.05). With
PAV, PCO2 decreased and V-T increased significantly only at L-4 whereas
PO2 increased from L-1 to L-4. Runaways were observed at L-3 and L-4 of
PAV. The pressure-time product (PTP) was determined for effective and
missing breaths. The mean total PTP per minute (of effective plus
missing breaths) was 160 +/- 57 cm H2O/s.min in PSV and 194 +/- 60 cm
H2O/s.min in PAV. Conclusion: We conclude that in COPD patients with
hypercapnic ARF, with increasing support, PSV causes the appearance of
ME whereas PAV develops runaway phenomena, due to the different
patient-ventilator interaction; however, these do not limit the
improvement of blood gases with the application of both methods.
Copyright (C) 2003 S. Karger AG, Basel.
Συγγραφείς:
Passam, F
Hoing, S
Prinianakis, G
Siafakas, N and
Milic-Emili, J
Georgopoulos, D
